The two cranes above began whooping as we watched, not knowing why they suddenly
stopped foraging and started making quite a fuss. Fortunately, we realized before
it was too late to get a shot that they were warning off the two whoopers below
that were flying through the territory claimed by the two above...

Whooping cranes, with a wingspan of 7.5 feet (2.3 meters),
are North America's tallest bird, standing nearly 5 feet (1.5 meters).

Photographed in the Aransas National Wildlife Refuge north of Fulton, Texas USA.